This invention relates generally to a check valve for use in a fluid conduit and more particularly to an improved swing check valve for use in sanitary sewer systems and the like.
A wide variety of check valves are available to permit fluid to flow in one direction in a conduit but to prevent it from flowing in the other. When used in sanitary sewer systems or similar applications such valves must exhibit a high degree of reliability and a resistance to clogging and corrosion. They should be relatively compact and ideally should be usable in vertical as well as horizontal conduits. Also, they should be relatively inexpensive to manufacture and easy to repair.
Among the check valves presently in use for such applications are of the butterfly and split valve types. While these valves perform adequately under some circumstances, they have a tendency to malfunction when the fluids passing through them contain sand or fibrous materials. They also cause a relatively high pressure loss due to the presence of the valve support structure in the fluid passageway. Swing type check valves have also been used with some success, but many of those presently available are relatively large and cause a substantial pressure drop in the fluid. Also, many are usable only in a horizontal conduit.
In an effort to eliminate the deficiencies of the check valves found in the prior art the inventor herein developed the valve described in U.S. Pat. No. 3,612,097, which was issued on Oct. 12, 1971. The valve disclosed in that patent represents a definite advance in the state of the art and has achieved significant commercial success. Experience with the device, however, has indicated that certain modifications and improvements are desirable. Under some flow conditions the valve tended to spin when open, resulting in undesirable amount of wear on the rivet used to join the valve and arm. Also, the pressed in valve seat protruded radially inward of the inner wall of the flow passageway to facilitate removal, but tended to cause debris to collect upstream of the seat and interfere with seating. In an effort to resolve these problems and to further improve the patented valve the present invention was made.